Modern inventory systems, such as those in mail-order and e-commerce warehouses, airport luggage systems, and custom-order manufacturing facilities, face significant challenges in providing fast, accurate responses to requests for inventory items. In recent years, automation has improved the speed and efficiency of storing and retrieving inventory items within such systems. However, automated systems can be extremely vulnerable to operational errors. In particular, when components within an automated system deviate from their anticipated operation, errors may be introduced. Correcting such errors may require manual intervention on the part of a human operator, thereby limiting the benefits of automation.